I picked up this book recently (actually I ordered it in the US and had it delivered to me here in Austria):
Self-Discipline in 10 days
Amazon.com: Self-Discipline in 10 Days: How to Go from Thinking to Doing: Books: Theodore Bryant
Someone here recommended it and I am absolutely surprised about its usefulness. I wouldn't have expected that because of this cheesy title. It's rather slim but a real gem.
Another good book is the Habit of Now